1. Field of the Invention
The present invention relates to a transfer foil for use in printing a pattern on a golf ball body, and to a golf ball printed with a pattern using the transfer foil, a method of printing a pattern with use of the transfer foil, and a method of manufacturing such a golf ball.
2. Description of the Related Art
A thermal transfer method using a transfer foil is employed in printing a pattern on a surface of a golf ball body. The typical transfer foil comprises a strip-like base film, and an ink layer carrying a predetermined pattern on one surface of the base film.
A conventional transfer foil had a release varnish layer between the base film and the ink layer. In case of printing a pattern on a surface of a ball body using the conventional transfer foil, the release varnish was also transferred when transferring the pattern carried by the ink layer to the surface of the ball body. The release varnish adhered to the surface of a transferred pattern on the ball body surface causes reduced adherence between the ball body surface and a topcoat thereon. To solve such a problem, various sorts of transfer foils without the need for release varnish have been proposed.
For example, Japanese Unexamined Patent Publication No. 57-69087 proposes a transfer foil having an ink layer which comprises a basic resin containing nitrocellulose and an alkyd resin, and a pigment or a dye as a coloring agent. Such an ink composition exhibits a good transferability, and therefor the ink allows the ink layer to be formed directly on the surface of the base film without a release varnish. However, a pattern carried by the ink layer can not be transferred at a temperature below 180° C.
Japanese Unexamined Patent Publication No. 58-183286 discloses a transfer foil having an ink layer containing a basic resin which comprises nitrocellulose and a resin selected from the group consisting of a polyamide resin, a hard resin, an acrylic resin, a polyester resin and a polyurethane resin. Using this transfer foil achieves transferring a pattern by pressing the transfer foil against a golf ball body surface for one second at 160° C. using a presser made of silicone rubber. However the temperature of 160° C. is still high for golf ball body having a cover made from a thermoplastic resin such as an ionomer. When the thermoplastic resin covered ball body is subjected to such a high temperature, dimples formed on the ball body surface are likely to be deformed, or in extreme cases the golf ball body itself may become deformed, which significantly affects the performance of the golf ball.
Japanese Unexamined Patent Publication No. 7-89214 proposes a transfer foil having an ink layer of which the basic resin is a polyurethane having a hydroxyl value ranging between 0.2 and 15. This transfer foil achieves transfer printing at 130° C. using a flat presser made of rubber. Further, the transfer foil can provide a good transferred pattern on the ball body surface suitable for a top coat This is because the hydroxyl group of the polyurethane resin contained in the ink layer reacts with the isocyanate contained in the two-pack polyurethane coating material to impart a higher strength to the transferred pattern. However, it is still possible that a golf ball having a cover made from a thermoplastic resin such as an ionomer becomes deformed at its dimples or its overall configuration when subjected to the temperature of 130° C.
The one transfer foil which achieves transfer printing at a temperature below 130° C. is only disclosed in Japanese Unexamined Patent Publication No. 11-139095. The basic resin forming the ink layer of this transfer foil contains a polyurethane having a hydroxyl value of less than 0.2 (inclusive of zero) and at least one of a polyester resin and an epoxy resin each having a hydroxyl value ranging between 60 and 250.